The present invention relates to a press brake and more particularly to a press brake having control wear linkages whereby the press brake is continuously displaced in parallel relationship with the bed to ensure quality workmanship on metal pieces being formed by the press brake.
In my earlier U.S. Pat. No. 3,587,286, there is disclosed a press brake for cold forming of sheet metals. However, we have found that with such a machine design, maintenance is often required due to backlash on the connecting rod bushings which cause the rim to tilt due to the uneven amount of wear of the pivot connections of the linkages on both sides of the ram. We have discovered that the fact that the linkages on each side of the ram differ in number, the sum of bushing wear on one side differs from the sum of bushing wear on the other side. Accordingly, this causes the ram to tilt out of parallelism with the bed. To remedy this problem, it is necessary to change the pins and bushings frequently.
Leveling adjustments of press brakes has been a problem in the industry for many years. There have been several attempts to provide leveling mechanisms to remedy this problem and such are disclosed, for example, in U.S. Pat. No. 3,763,690 and 4,070,896. However, these leveling devices have proven costly and also require periodic maintenance and adjustments to ensure precise parallel movement between the ram and the bed.
It is a feature of the present invention to provide a press brake which substantially overcomes the above-mentioned disadvantages of the prior art in a simple, economical and effective manner.
Another feature of the present invention is to provide a press brake which provides substantially balanced wear of the pivot connections on opposed sides of the ram and wherein this is achieved by providing symmetrical linkage assemblies on opposed sides of the ram so that the wear on both sides of the ram is substantially the same and therefore the backlash in the connecting rod bushings is subtractive, that is the ram will tilt only in proportion to the difference in the actual backlash, rather than the sum.
Another feature of the present invention is to provide a press brake and wherein the ram is displaced substantially in perfect parallel relationship with the bed even if the pivot connections of the linkages are subjected to wear.
According to the above features, from a broad aspect, the present invention provides a press brake comprising a frame, a bed formed on the frame, and a ram displaceable to and away from the bed in a vertical plane. The ram has a lower metal working straight edge disposed parallel to the bed. The ram is displaceable by ram displacement means secured to the ram by opposed symmetrical linkage assemblies. Each of the linkage assemblies are connected adjacent opposed ends of the ram. Each of the linkage assemblies also include a lever member pivotally secured to the frame by an anchor pin pivot connection. A link arm interconnects the lever member to the ram by pivot pin connections adjacent opposed ends of the link arm. An interconnecting bar interconnects the lever member of each of the linkage assemblies together by a further pivot pin connection adjacent opposed ends of the interconnecting bar. The ram displacement means has a pivot pin connection with the interconnecting bar whereby to displace the interconnecting bar to cause the linkage assemblies to pivot in unison on their anchor pin pivot connection to cause the ram working straight edge to be displaced in substantially perfect parallel relationship with the bed. The symmetrical linkage assemblies have identical pivot pin and anchor pin connections whereby wear of the connections during operation is substantially the same on opposed sides of the ram whereby backlash in said pin connections is subtractive to minimize ram tilt and ensure substantially continuous parallel displacement thereof.